One look at the documentation would have told you, that collisions are handled per fixture. Obviously your bumpers consist of more than one fixture. You only check against the first one in all cases though:

if (Bumper == bumperRight[0])

You also have to check against bumperRight[1..n] here. Please try to understand the basics of bodies, fixtures, and shapes, before jumping into advanced stuff like Texture2Fixture conversion without knowing what you are doing.